The present invention relates generally to solution concentration monitoring systems and coating apparatus incorporating same and more particularly to such coating apparatus which is designed to continuously monitor and maintain the concentration level of the coating solution and to enable complete coating of all exposed surfaces of the workpiece.
There exists a wide variety of both applications wherein it is necessary or desirable to apply a coating to workpiece and apparatus for applying same. In some instances it is desirable to apply the coating by immersing the workpiece in a dip tank or the like such as for example in applying lubricants to a billet which is to be forged into a finished form. In such applications it is very important to insure all surfaces of the part are fully coated so as to assure uniform metal flow during the forming process. It also is important to maintain the proper level of concentration of the lubricant in the coating solution at all times. While the rate of consumption of the lubricant may be easily determined on the basis of the number of workpieces being processed, the control of the carrying vehicle or solvent which may be subject to evaporative losses as well as loss from workpiece carry over is much more difficult as such losses depend upon a wide variety of continuously changing conditions such as temperature, relative humidity, air flow in the treating area, etc. For example, one form of such a lubricant comprises an aqueous colloidal dispersion. Rate of loss of such water solvent may depend upon all of the above factors including the temperature of the bath itself.
Additionally, in order to promote more efficient manufacturing of forged parts, efforts are being made to reduce the number of steps in the forging process. One way in which this is accomplished is by fabricating a preformed billet or workpiece so as to reduce the amount of metal flow which must be accomplished during the forming operation. Obviously in such applications, the necessity for insuring that a complete coating of lubricant is applied to the workpiece is particularly important. Further compounding this problem is that because the workpiece is preformed prior to coating, extreme care must be exercised in the handling thereof so as to avoid chipping, nicking, wearing or otherwise damaging of corners, edges, or other surfaces thereof as such damage may result in formation of an unacceptable finished part. This need for careful handling precludes the use of tumbling type coating apparatus wherein a plurality of parts are immersed in batch form. Further, the use of conveyor apparatus, be it a type supporting a part from below or above, results in the contacted portions of the workpiece being inadequately or totally uncoated.